underside
nounUK /ˈʌndəsaɪd/
US /ˈʌndərsaɪd/
The underside is the bottom part of something.
The underside of the leaf was soft and fuzzy.
OTHER MEANINGS
2. The side of a vehicle or object that faces the ground.
He checked the underside of the car for rust.
3. The hidden or less visible part of a situation.
The underside of the deal was not revealed to the public.
4. The lower surface of an animal's body.
The turtle's underside is protected by a hard shell.